The idea of a large metal mass accelerator often called an electromagnetic launcher (EML) was demonstrated in the late 1800's and utilized the repulsion between two current carrying loops. This type of launcher is still used to illustrate the electromagnetic repulsion phenomena in basic physics classes today. The use of these EML's as guns was shown around the turn of the century and consisted of multiple coil solenoidal accelerators and laminated iron projectiles. Numerous attempts to produce large solid projectile guns with this method failed because of the difficulty of generating and switching the large amounts of power required.
Another class of known EML's used to accelerate projectiles is the rail gun. This apparatus consists of two parallel conducting rails with a sliding conductor. The projectile is placed perpendicular to, and in contact with, the rails. A current, passing from one rail through the sliding conductor and then through the second rail, generates a magnetic field which acts on the sliding conductor to push and accelerate it along the rails.
This apparatus requires high current levels and suffers from sliding conductor problems, as the metal to metal contact is not reliable and leads to severe arcing. The next advancement to the railgun was to use a plasma. This replaced the sliding metal contact and propelled the projectile. Modern railgun research has been principally in this area.
A relatively recent improvement to the railgun is the coaxial plasma gun. Coaxial electrodes utilizing high energy capacitive discharges have existed since the early 1960's. Such devices, usually operated at a reduced atmosphere, use a static gas prefill or a "puffed" gas as the working material to generate the plasma. Energy, in for example a capacitor bank, is connected across the electrodes, causes the gas to breakdown, and forms a highly ionized plasma which is accelerated down the gun by the resulting Lorentz forces. Such electromagnetic plasma accelerators were intensively developed in the 1960's, principally for two applications: propulsion and nuclear fusion. The goal of this work was to efficiently produce high velocity pulsed plasma. Prefill gas systems lead to dense plasma focus which is useful for fusion applications. Puffed gas systems produce a directed slug of plasma and are useful in space thruster applications. Development has continued in these areas with added applications for high power switches and as a source of x-rays, ions, and electrons.
A. Feugeas, et al, "Nitrogen Implantation of AISI 304 Stainless Steel with a Coaxial Plasma Gun", J. Appl. Phys. 64, (5), September, 1988, p. 2648, described such a coaxial plasma gun used as an ion implanter, and showed that the resulting implanted stainless steel had better wear properties than the untreated material.
M. Sokolowski, "Deposition of Wurtzite Type Boron Nitride Layers by Reactive Pulse Plasma Crystallization," J. Crystal Growth, 46, 1979, p. 136, describes a scientific study on the use of a coaxial plasma generator to crystallize thin layers of boron nitride.
Ion implantation has been used for some time to modify the surface properties of various materials such as metals, polymers, and coatings. The use of directed energetic ion beams to improve adhesion, create texture, enhance wear or scratch resistance, make polymers conductive, and increase optical transmission has been reported. Ion implantation has not been used for improving adhesion by melting an underlying semicrystalline polymer. Ion implantation cross-links or degrades the polymer without melting.
Other surface modification processes are well known. For example E-beam, corona and plasma treatment have been used to increase the adhesion of coatings to surfaces, etch material, and change the chemistry of the surface. These methods, as well as ion implantation, are either continuous or long pulse length processes, their low energy flux results in a low heat transfer rate, and as such they are not appropriate for surface modification as exemplified by the present invention. Most of these treatments affect polymer surfaces in a fairly gross manner, and any thermal modification which takes place, affects the bulk of the polymer and not just the surface. The process of the present invention is an advance over these earlier processes of surface modification because its short pulse length, high fluence, and high intensity allow a thin surface treatment of a material and thus do not affect the bulk physical or chemical properties of the material.
U.S. Pat. No. 4,822,451 (Ouderkirk et al) teaches a process for the surface modification of semi-crystalline polymers wherein said polymers can have predetermined amounts of their surfaces rendered quasi-amorphous by irradiation with high energy pulses, such as for example an excimer laser. This process essentially teaches energy transfer alone (the greatest particle mass being e-beam irradiation).
"Comparative Status of Pulsed Ion Implantation", J. Gyulai and I. Krafcsik, Nuclear Instruments and Methods in Physics Research B37/38 (1989) pp 275-279 describes an experimental exploration of the effects of pulsed ions on doping and annealing of materials. Metals, ceramics and organics are considered as targets for the pulsed ions. Generally at least one thousand pulses were used and the study used primarily boron ions. The work is primarily performed on metal surfaces and semiconductive surfaces, although organic surfaces are generally described.